This invention is generally directed to photoresponsive imaging members, and more specifically the present invention is directed to layered photoresponsive members having incorporated therein certain perylene pigment compositions. Thus, in one embodiment the present invention envisions the use of specific pigment compositions as organic photogenerator materials in photoresponsive imaging members containing therein arylamine hole transport molecules. The aforementioned photoresponsive imaging members can be negatively charged when the perylene photogenerating layer is situated between the hole transport layer and the substrate; or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. Additionally, the photoresponsive imaging members with the perylene pigment compositions as photogenerator substances, and wherein the member further includes therein an aryl amine hole transport layer are useful in electrophotographic imaging processes, especially xerographic processes wherein negatively charged or positively charged images are rendered visible with developer compositions of the appropriate charge.
Layered photoresponsive imaging members are generally known, reference for example U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference, wherein there is described an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of substances useful in the photogenerating layer of this patent include trigonal selenium, metal phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles. Accordingly, as a result the photoconductive particles must be in a substantially contiguous particle-to-particle contact throughout the layer for the purpose of permitting charge dissipation required for the cyclic operation. With a uniform dispersion of photoconductive particles a relatively high volume concentration of photoconductor material, about 50 percent by volume, is usually necessary to obtain sufficient photoconductor particle-to-particle contact for rapid discharge. This high photoconductive loading can result in destroying the physical continuity of the resinous binder, thus significantly reducing the mechanical properties thereof. Illustrative examples of specific binder materials disclosed in the '006 patent include polycarbonate resins, polyester resins, polyamide resins, and the like.
Many other patents are in existence describing photoresponsive devices including layered devices containing generating substances, such as U.S. Pat. No. 3,041,167, which discloses an overcoated imaging member with a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member is utilized in an electrophotographic copying method by, for example, initially charging the member with an electrostatic charge of a first polarity, and imagewise exposing to form an electrostatic latent image which can be subsequently developed to form a visible image. Prior to each succeeding imaging cycle, the imaging member can be charged with an electrostatic charge of a second polarity, which is opposite in polarity to the first polarity. Sufficient additional charges of the second polarity are applied so as to create across the member a net electrical field of the second polarity. Simultaneously, mobile charges of the first polarity are created in the photoconductive layer such as by applying an electrical potential to the conductive substrate. The imaging potential which is developed to form the visible image is present across the photoconductive layer and the overcoating layer.
Photoresponsive imaging members with squaraine photogenerating pigments are also known, reference U.S. Pat. No. 4,415,639. In this patent there is illustrated an improved photoresponsive imaging member with a substrate, a hole blocking layer, an optional adhesive interface layer, an organic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, and a hole transport layer. As photoconductive compositions for the aforementioned member there can be selected various squaraine pigments, including hydroxy squaraine compositions. Moreover, there is disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrostatographic imaging processes.
The use of selected perylene pigments as photoconductive substances is also known. There is thus described in Hoechst European Patent Publication Nos. 0040402, DE3019326, filed May 21, 1980, the use of N,N'-disubstituted perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive substances. Specifically, there is disclosed in this publication evaporated N,N'-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyldiimide dual layered negatively charged photoreceptors with improved spectral response in the wavelength region of 400 to 700 nanometers. A similar disclosure is revealed in Ernst Gunther Schlosser, Journal of Applied Photographic Engineering, Vol. 4, No. 3, page 118 (1978). There is also disclosed in U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance with the teachings of this patent the photoconductive layer is preferably formed by vapor depositing the dyestuff in a vacuum. Also, there is specifically disclosed in this patent dual layer photoreceptors with perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have spectral response in the wavelength region of from 400 to 600 nanometers.
Moreover, there is disclosed in U.S. Pat. No. 4,419,427 electrographic recording mediums with a photosemiconductive double layer comprised of a first layer containing charge carrier perylene diimide producing dyes, and a second layer with one or more compounds which are charge transporting materials when exposed to light, reference the disclosure in column 2, beginning at line 20. Also of interest with respect to this patent is the background information included in columns 1 and 2, wherein perylene dyes of the formula illustrated are presented.
Furthermore, there is presented in copending application U.S. Ser. No. 587,483, now U.S. Pat. No. 4,514,482 entitled Photoconductive Devices Containing Perylene Dye Compositions, the disclosure of which is totally incorporated herein by reference, an ambipolar imaging member comprised of a supporting substrate, a photoconductive layer comprised of specific perylene dyes different than the perylene pigments of the present invention, which dyes are dispersed in a polymeric resinous binder composition; and as a top layer a specific aryl amine hole transporting substance dispersed in an inactive resinous binder. Examples of perylene dyes selected for the photoconductive layer of the copending application include N,N'-di(2,4,6-trimethylphenyl)perylene 3,4,9,10-tetracarboxyldiimide, N,N'-di(2,4,6-trimethoxyphenyl)perylene 3,4,9,10-tetracarboxyldiimide, and N,N'-di(2,6-dimethylphenyl)perylene 3,4,9,10-tetracarboxyldiimide.
Additionally, there is disclosed in U.S. Pat. No. 4,429,029 electrophotographic recording members with perylene charge carrier producing dyes and a charge carrier transporting layer. The dyes selected, which are illustrated in column 2, beginning at line 55, are substantially similar to the photogenerating dyes of the present invention. The aryl amine hole transporting compounds selected for members of the present invention are, however, not described in the U.S. Pat. No. 4,429,029 patent; and further with the photoresponsive imaging members of the present invention the photogenerating perylene layers are prepared by vacuum deposition enabling superior image quality in comparison to the binder or binderless dispersed layers obtained by the spray coating or solution casting techniques as illustrated in the U.S. Pat. No. 4,429,029 patent. Vacuum deposition enables, for example, layers of uniform thickness and substantial smoothness, as contrasted to layers of ununiform thickness and surface roughness with binder or binderless dispersed layers prepared by spray coating processes; very thin layers of 0.1 microns or less are permitted whereas with binder or binderless dispersed layers, thicknesses are generally about 0.5 microns or more; and continuous layers with no large voids or holes result, while dispersed layers usually contain holes or voids thereby adversely affecting image resolution.
Furthermore, with the imaging members of the present invention comprised of vacuum deposited perylenes, and aryl amine holes transporting compounds superior xerographic performance occurs as low dark decay characteristics result and higher photosensitivity is generated, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example, U.S. Pat. No. 4,429,029 mentioned hereinbefore.
While the above-described photoresponsive imaging members are suitable for their intended purposes, there continues to be a need for improved members, particularly layered members, having incorporated therein specific perylene pigment compositions and aryl amine hole transport compounds. Additionally, there continues to be a need for layered imaging members comprised of specific aryl amine charge transport compositions; and as photogenerating materials perylene pigments with acceptable visible sensitivity, low dark decay characteristics, high charge acceptance values, and wherein these members can be used for a number of imaging cycles in a xerographic imaging or printing apparatus. Furthermore, there continues to be a need for photoresponsive imaging members which can be positively or negatively charged thus permitting the development of images, including color images, with positively or negatively charged toner compositions. Moreover, there continues to be an important need for disposable imaging members with nontoxic organic pigments. Also, there is a need for disposable imaging members useful in xerographic imaging processes, and xerographic printing systems wherein, for example, light emitting diodes (LED), helium cadmium, or helium neon lasers are selected; and wherein these members are particularly sensitive to the visible region of the spectrum, that is, from about 400 to about 800 nanometers.